I have a 3g and updated to 4.0 a few days ago. I had a few issues initially but was able to overcome those using redsn0w (b5 vice 4). I did notice that my world clock was missing from the springboard though; more importantly for me was the alarm which I use everyday. I read a few suggestions to restore and select as new phone. I tried this to no avail along with a couple other restores using various combinations. I tried downloading the firmware and using it vice the 4.0 update through iTunes and got the same results. I know it probably sounds ridiculous but this is a big issue for lol.

Any suggestions? Oh, it is missing prior to the jailbreak and doesnt magically reappear after.